polymers Article Structural Integrity of Polymeric Components Produced by Additive Manufacturing (AM)—Polymer Applications Rui F. Martins 1, * , Ricardo Branco 2 , Filippo Berto 3 , Nuno Soares 4 and Sebastião Bandeira 4   Citation: Martins, R.F.; Branco, R.; Berto, F.; Soares, N.; Bandeira, S. Structural Integrity of Polymeric Components Produced by Additive Manufacturing (AM)—Polymer Applications. Polymers 2021, 13, 4420. https://doi.org/10.3390/ polym13244420 Academic Editor: Antonio Gloria Received: 17 October 2021 Accepted: 14 December 2021 Published: 16 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 UNIDEMI, Department of Mechanical and Industrial Engineering, Nova School of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal 2 CEMMPRE, Department of Mechanical Engineering, Faculty of Sciences and Technology, University of Coimbra, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra, Portugal; ricardo.branco@dem.uc.pt 3 Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway; filippo.berto@ntnu.no 4 Department of Mechanical and Industrial Engineering, Nova School of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal; ng.soares@campus.fct.unl.pt (N.S.); s.bandeira@campus.fct.unl.pt (S.B.) * Correspondence: rfspm@fct.unl.pt; Tel.: +351-212-948-567 Abstract: In the work presented herein, the structural integrity of polymeric functional components made of Nylon-645 and Polylactic acid (PLA) produced by additive manufacturing (Fused Deposition Modelling, FDM) is studied. The PLA component under study was selected from the production line of a brewing company, and it was redesigned and analyzed using the Finite Element Method, 3D printed, and installed under real service. The results obtained indicated that, even though the durability of the 3D printed part was lower than the original, savings of about EUR 7000 a year could be achieved for the component studied. Moreover, it was shown that widespread use of AM with other specific PLA components could result in even more significant savings. Additionally, a metallic hanger (2700 kg/m 3 ) from the cockpit of an airplane ATR 70 series 500 was successfully redesigned and additively manufactured in Nylon 645, resulting in a mass reduction of approximately 60% while maintaining its fit-for-purpose. Therefore, the components produced by FDM were used as fully functional components rather than prototype models, which is frequently stated as a major constraint of the FDM process. Keywords: polymers; additive manufacturing; structural integrity; PLA; Nylon-645 1. Introduction Polymers, either in their natural or synthetic form, thermoplastic or thermosetting, can be considered cheap materials, characterised by low density and diverse characteristics of mechanical resistance, ductility, toughness, and viscoelasticity, to mention a few. Their use has been rising tremendously since the 1960s [1], replacing steel and glass, and through the introduction of an extensive list of new synthetic polymers in final products, generally obtained by injection molding. This growth was further enhanced in recent years with the massive use of the Fused Deposition Modelling (FDM) process. FDM is one of the most popular additive manufacturing (AM) technologies for var- ious engineering applications and was introduced commercially in the early 1990s by Stratasys Inc., USA. It is a Material Extrusion (ME) technique [2] that fabricates parts using a softened or melted thermoplastic filament form material continuously extruded through a nozzle, layer-upon-layer, based on 3D computer-aided design (CAD) instead of subtractive manufacturing methodologies [3]. In fact, since its invention, the impact of AM has continued to grow in both commercial and scholarly activities due to the processing of several types of polymers, and, more recently, metals. Therefore, this technology is shifting from prototyping to a dominant production industry, although limited so far to the Polymers 2021, 13, 4420. https://doi.org/10.3390/polym13244420 https://www.mdpi.com/journal/polymers